The present invention relates to a cleaning mechanism and a cleaning method, which are adapted for cleaning the probe needles of a probing apparatus used for inspecting the electric characteristics of an object under electrical inspection.
A large number of semiconductor devices (hereinafter referred to as chips) formed on a semiconductor wafer (hereinafter referred to simply as a wafer) are an example of the object that should be inspected by the subject apparatus. A probing apparatus is employed to inspect the electric characteristics of the chips formed on the wafer.
For inspection, the wafer is placed on the main chuck, which is arranged inside the apparatus and movable in the X, Y, Z and .theta. directions. The wafer is index-fed by moving the main chuck. As shown in FIG. 6, the probe needles 1 of a probe card are brought into contact with the electrode pads (not shown) of the chips on the wafer that is being index-fed during inspection. The electrodes of the chips are electrically connected to a tester, so as to inspect the electric characteristics of the chips.
In order to achieve reliable electric connection between the probe needles 1 and the electrode pads, the electrode pads, which are formed of aluminum, must be processed to remove a natural oxide film therefrom. The natural oxide film on the electrode pads is scraped off by using of the probe needles 1.
However, if this inspection process is repeated, aluminum oxide or other undesirable substance will adhere to the tips of the probe needle 1. If such undesirable substance as aluminum oxide is present, the probe needles 1 may not be electrically connected to the electrode pads of the chips. To solve this problem, the conventional art employs a main chuck provided with an abrasive plate. The tip ends of the probe needles 1 are cleaned by means of the abrasive plate, for the elimination of adherent substance.
FIG. 6 shows a structure wherein a plurality of probe needles 1 are supported on a probe card at one end. The probe needles 1 are arranged in such a manner that they can be simultaneously brought into contact with the electrodes arranged in rows.
However, the conventional cleaning method has the problem that the substance adherent to the abrasive plate will scatter at the time of polishing. In addition, the abrasive plate is horizontally projected from the wafer chuck. Due to this structure, in order to polish all probe needles 1 by use of the same abrasive plate, the wafer chuck has to be moved greatly in such a manner that the probe needles are all brought into contact with the abrasive plate without exception. As long as the moving range of the wafer chuck is wide, the apparatus is inevitably large in size.
The present applicant developed a technique for preventing generation of particles, such as those generated when the substance adherent to the probe needles is removed and scattered, and filed a patent application to claim that technique (Japanese Patent Application No. 9-106616). The technique is directed to a soft cleaner 2 comprising a cleaner layer that is formed of rubber and inorganic filler (see FIG. 7). The present applicant also developed a cleaning mechanism comprising a brush cleaner (not shown) that has a cleaner layer, and filed a patent application (Japanese Patent Application No. 9-220247). This cleaning mechanism enables all probe needles of a probe card to be cleaned, with no need to provide a wide space inside the apparatus.
A further study was made of the soft cleaner and brush cleaner described above, and it was found out that the cleaners needed improvement in the following points. In the case where the soft cleaner 2 is employed, the probe needles 1 are stabbed into the soft cleaner 2, as shown in FIG. 7. At the time, the substance D adherent to the surface of the probe needles, such as abraded particles, are rubbed off the surface and collected in the neighborhood of the upper portion of the probe needles. However, such substance may partially remain on the probe needles 1. Moreover, it should be noted that the surfaces of the probe needles 1 have been subjected to sand blast processing, as shown in FIG. 8. When the substance D is cleaned away from the tiny depressions formed in the surface of the probe needles by means of the brush cleaner, the tip ends of the bristles of the brush are bent, as shown in FIG. 8. Since the bristles are soft in this manner, the substances in the tiny depressions cannot be fully removed.
In the case where a probe card that supports probe needles 1A upright is employed, the substance D from the electrode pads will adhere not only to the probe needles 1A but also to the support plate 2A used for supporting them. However, the substance D adherent to the support plate 2A cannot be removed therefrom by means of the soft cleaner or brush cleaner described above. The remaining substance D may come off the support plate 2A and drop onto a wafer under inspection, resulting in unreliable examination.